The present invention relates to a rotary vane compressor. Such compressors are well known in the art and are widely used in refrigeration and air conditioning systems and the like due to their many advantages. These compressors comprise a cylinder formed with a bore and an inlet and outlet communicating with the bore. A rotor is disposed in the bore and formed with a plurality of radial grooves or slots in which vanes are slidably disposed. The vanes are urged by centrifugal force, spring force, oil pressure or a combination thereof into sealing engagement with the inner wall of the bore. The bore may be non-circular and the rotor mounted coaxially therein. Alternatively, the bore may be circular and the rotor mounted eccentrically therein. In either case, rotation of the rotor and vanes as an integral unit causes compressive displacement of refrigerant or other fluid from the inlet to the outlet through the bore since the rotating vanes define pressure chambers of changing volume.
It is advantageous to apply a fluid lubricant such as oil to the inner ends of the vanes under pressure and provide a clearance between the sides of the vanes and the adjacent walls of the slots. The oil serves the dual function of urging the vanes against the wall of the bore and also penetrating through the clearances between the vanes and slots to lubricate the vanes and adjacent walls of the slots. The oil also serves to prevent leakage of refrigerant fluid past the vanes.
However, due to the frictional resistance between the outer edges of the vanes and the wall of the bore, the vanes are urged to tilt backwardly, or opposite to the direction of movement of the rotor. Due to the clearances between the vanes and slots, the trailing surfaces of the vanes pressingly engage with the sharp trailing outer edges of the slots. This produces frictional resistance to radial movement of the vanes in the slots and degrades the torque of the compressor. In addition, the sharp trailing outer edges of the slots scrape oil off the vanes, thereby increasing the coefficient of friction between the vanes and slots and thereby the frictional resistance to radial movement. This increased friction contributes to excessive wear of the vanes and slots and in the worst case situation may cause the vanes to freeze or stick in the slots, resulting in failure of the compressor.